This Physician Scientist Award has two Specific Aims. The first, to be accomplished in Phase I (years 1 & 2) is to develop intellectual and "hands-on" expertise in a broad range of areas involving cell biology, molecular biology, protein chemistry, and immunology. This will be accomplished by a combination of formal classroom study at the graduate student level, a series of rotations through well- equipped, state-of-the-art laboratories, and continued immersion in the laboratory. Phase II (years 3-5) will be devoted to three projects. Project 1 involves the complete protein chemical characterization of a novel carboxy-terminal secretory form of parathyroid hormone-related protein (PTHrP). This C-terminal species of PTHrP, which is predicted to exist by the endoproteolytic cleavage signals in the PTHrP initial translation product, has already been identified by the applicant. Project 2 is to clarify the roles of known endoproteolytic processing enzymes (furin, PC-2, etc.) in the post-translational processing of PTHrP. cDNA probes for all of the known processing endoproteases will be used to survey PTHrP-producing cell lines to determine whether they are candidates for authentic PTHrP processing enzymes. Project 3 seeks to identify and characterize a novel monobasic PTHrP processing endoprotease which appears to be present in the golgi of PTHrP-secreting cell lines. This monbasic-cleaving endoprotease(s) will be characterized with regard to intracellular location, substrate specificity,, Km, pH optimum, and inhibitor profile. PTHrP is a widely-expressed, highly-conserved neuroendocrine peptide which appears to undergo extensive post-translational processing. Collectively, these studies will shed insight into the post- translational processing patterns of PTHrP, and will further clarify the secretory forms of the peptide so that meaningful physiological studies can be undertaken.